JP3922760B2 - Fluid machinery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid machine, and in particular, an axial flow pump capable of easily obtaining a constant head characteristic suitable for a centrifugal pump and a feed water pump which can easily obtain a constant flow characteristic suitable for a circulation pump. The present invention relates to a fluid machine including
[0002]
[Prior art]
Conventionally, a spiral pump has been used as a hot / cold water circulation pump for heating and cooling. The important matters in this application are as follows.
(1) Even if the required flow rate is known, there is a subtle difference between the calculated piping loss and the actual piping loss, so it is necessary to adjust the flow rate with a valve on site. In this case, there is an energy loss corresponding to the loss of the valve.
(2) If the piping loss increases due to aging of the piping or clogging of foreign matter to the valve, the flow rate will decrease. Therefore, it is necessary to periodically adjust the flow rate with a valve or the like.
(3) Since there is generally no means for measuring the flow rate at the site, it is necessary to grasp the pressure with a pressure gauge and estimate the flow rate based on the pump characteristic curve. However, this method has low accuracy.
[0003]
Conventional techniques for solving these problems include those listed below.
(1) The electromagnetic flow meter signal is processed by the control panel to control the opening of the solenoid valve. This method is expensive and involves a loss of a valve, so that there is a disadvantage that the energy saving effect is low.
(2) Take the signal of the electromagnetic flowmeter into the frequency converter and run it at variable speed. This method saves energy but is expensive.
(3) A rotation speed switching knob is provided on the pump, and the QH characteristic of the pump is changed, and at the same time, a valve is used in parallel and used according to the required flow rate. This method has an effect of reducing energy loss due to the resistance of the valve, but has no effect of stabilizing the flow rate. Therefore, when there is an increase in piping loss, etc., it is necessary to adjust the flow rate each time.
[0004]
[Problems to be solved by the invention]
In view of the above-mentioned problems, the present invention has as a technical problem to provide a fluid machine such as a centrifugal pump that does not require special incidental equipment and always supplies a stable flow rate regardless of changes in pipe resistance. Yes.
Further, the present invention has a technical problem to provide a fluid machine such as an axial flow pump that is suitable as a water supply pump because the generated head is constant even when the flow rate is changed.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention is directed to a frequency converter that supplies electric power to a motor and a current that is supplied to the motor in a fluid machine that generates pressure by being driven by a motor and rotating an impeller . Detection means for detecting a current value , and a control unit provided in the frequency converter in which A = K Hz ⁿ (K and n are positive constants) , which is a relationship between the frequency ( Hz ) and the current value (A) , is stored in advance. The control unit compares the frequency and current value in actual operation with A = K Hz ⁿ , which is the relationship between the frequency ( Hz ) and the current value (A), and supplies it to the motor. and wherein the current value of the current is in so that by changing the occurrence frequency of the frequency converter to match the a = K Hz ^n, provided with means for switching the value of the K and n to the frequency converter for To do.
[0006]
In one aspect of the present invention, a fluid machine in which shaft power increases as the flow rate increases under the same rotational speed is used so that the flow rate becomes substantially constant even if the generated pressure changes.
In one aspect of the present invention, a fluid machine in which shaft power decreases as the flow rate increases under the same rotational speed is used so that the generated pressure becomes substantially constant even when the flow rate changes .
[0007]
Moreover, as a preferable aspect of the present invention , a spiral pump driven by a three-phase induction motor, a frequency converter that supplies power to the three-phase induction motor, and detection of a frequency and a current value provided in the frequency converter In the pump device comprising the means and a program that defines the relationship between the frequency and current value stored in the frequency converter, the frequency and current value in actual operation are compared with the specified program, and the pump the operating point so as to change the generated frequency of the frequency converter so as to be close to the specified program, lift of the pump be varied, the flow rate is set to be substantially the same.
In a preferred aspect of the present invention, the function of integrating the flow rate is provided by multiplying the time output by the frequency converter and the value of the constant flow rate.
As a preferred embodiment of the present invention, a flow rate display unit is provided in the frequency converter.
As a preferred embodiment of the present invention, the memory function of the frequency converter is utilized to carry out a work for transporting a predetermined amount of water every predetermined time continuously for a predetermined number of days, to pause for a predetermined number of days, and to perform a work continuously for a predetermined number of days. Automatic operation like this is possible.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a fluid machine according to the present invention will be described.
FIG. 1 is an explanatory diagram for explaining the basic concept of the present invention, and FIG. 1 (a) is a diagram showing the relationship between the flow rate (Q) and the head (H) of a centrifugal pump as an example of a fluid machine. (B) is a figure which expands and shows the I (b) part of Fig.1 (a). In FIG. 1A, the horizontal axis indicates the flow rate ratio, and the vertical axis indicates the head ratio. The motor for driving the centrifugal pump of the present invention includes an inverter. And the several knob (selection means) which selects a required flow volume is comprised.
[0009]
In FIG. 1, the frequency (Hz) and current value (A (ampere)) of the inverter are
Knob A A = 0.001 × Hz ² …… Flow rate ratio 0.7
Knob B A = 0.0014 × Hz ² ...... Flow ratio 1.0
A case where two types of memory are stored will be described as an example.
Now, it is assumed that knob B is selected.
At this time, it is assumed that the resistance curve of the pipe is (2) in FIG.
When the pump is activated, the pump is operated at a previously stored frequency of 100 Hz (6000 rpm). The operating point is the intersection α1 (100 Hz-15 A) with the resistance curve (2). This operating point has a higher current value compared to A = 0.0014 Hz ² (A = 0.0014 × 100 ² = 14 A) stored in advance. That is, for a frequency of 100 Hz, this means that the current value is excessive.
[0010]
Therefore, the inverter is decelerated to match the frequency and current value to A = 0.0014 Hz ² . That is, the operation is performed at a reduced frequency.
Next, it is assumed that the pump is operated at 90 Hz as a result of deceleration. The operating point is the intersection β1 (90 Hz-10 A) with the resistance curve (2). This operating point has a lower current value than A = 0.0014 Hz ² (A = 0.0014 × 90 ² = 11.34 A) stored in advance. That is, for a frequency of 90 Hz, it means that the current value is too small.
[0011]
Therefore, the inverter operates at a higher speed so that the frequency and the current value are adjusted to A = 0.0014 Hz ² . In other words, the frequency is increased.
As a result of the above, the pump is operated at the point γ1 of A = 0.0014 × 95 ² ≈12.5 A (95 Hz-12.5 A).
That is, the operation is performed according to the flow rate of the selected knob B. If this method is used, the pump is operated at a constant flow rate and operated with the minimum necessary power consumption regardless of the magnitude and fluctuation of the pipe resistance, and is optimal for the circulation pump.
Note that the point δ described as a true essential point in FIG. 1 is an operating point for supplying the most suitable amount of heat when used for circulating hot water, for example. This point may slightly deviate from the amount of operating heat calculated in advance. This is to allow a margin in calculation.
[0012]
In order to solve this problem, the types of inverter flow rate selection knobs that can be selected can be increased (for example, about eight types instead of two types A and B as shown in FIG. 1).
The above is an example of a centrifugal pump in which shaft power (power consumption and current value) increases as the flow rate increases at a constant rotational speed (constant frequency (Hz)).
[0013]
FIG. 2 is an explanatory diagram showing an example in which an axial pump whose axial power decreases as the flow rate increases at a constant rotational speed (a constant frequency (Hz)) is controlled at a constant pressure. In FIG. 2, the horizontal axis represents the flow ratio, and the vertical axis represents the head ratio.
[0014]
In FIG. 2, the frequency (Hz) and current value (A (ampere)) of the inverter are
A = 0.0012 × Hz ² …… Head ratio 0.75
A case where the data is stored in the memory will be described as an example.
At this time, the resistance curve of the pipe is assumed to be (1) in FIG.
When the pump is activated, the pump is operated at a previously stored frequency of 100 Hz (6000 rpm). The operating point is the intersection α2 (100 Hz-14 A) with the resistance curve (1). This operating point has a higher current value as compared to A = 0.0012 × Hz ² (A = 0.0012 × 100 ² = 12 A) stored in advance. That is, for a frequency of 100 Hz, this means that the current value is excessive.
[0015]
Therefore, the inverter is decelerated to match the frequency and current value to A = 0.0012 Hz ² . That is, the operation is performed at a reduced frequency.
Next, it is assumed that the pump is operated at 90 Hz as a result of deceleration. The operating point is the intersection β2 (90 Hz-9A) with the resistance curve (1). This operating point has a low current value as compared to A = 0.0012 Hz ² (A = 0.0012 × 90 ² = 9.72 A) stored in advance. That is, for a frequency of 90 Hz, it means that the current value is too small.
[0016]
Therefore, the inverter operates at a higher speed so that the frequency and the current value are adjusted to A = 0.0012 Hz ² . In other words, the frequency is increased.
As a result of the above, the pump is operated at the point of A = 0.0012 × 95 ² A≈11 A (95 Hz-11 A). That is, it operates with the selected pressure. When this method is used, the pump is operated at a constant pressure (lift) and operated with the minimum necessary power consumption regardless of the magnitude and fluctuation of the pipe resistance, and therefore, it is suitable as a water supply pump.
[0017]
As shown in FIGS. 1 and 2, according to the present invention, the flow rate or pressure can be kept constant with a single pump without using an electromagnetic flow meter, pressure gauge (or pressure sensor), etc. Does not require any special equipment and does not require the adjustment of valves.
[0018]
FIG. 3 shows a preferred pump apparatus for carrying out the present invention. This pump device is an all-around canned motor pump in which a handling liquid flows around the motor.
[0019]
The all-around flow type canned motor pump shown in this embodiment includes a pump casing 1, a canned motor 6 accommodated in the pump casing 1, and an impeller 8 fixed to an end of a main shaft 7 of the canned motor 6. And. The pump casing 1 includes a pump casing outer cylinder (barrel) 2, a suction casing 3 connected to both ends of the pump casing outer cylinder 2, and a discharge casing 4. The suction casing 3 is connected to the outer cylinder 2 by welding, and the discharge casing 4 is connected to the outer cylinder 2 by flanges 61 and 62. The pump casing outer cylinder 2, the suction casing 3, and the discharge casing 4 are formed of sheet metal made of stainless steel or the like.
[0020]
On the other hand, the canned motor 6 includes a stator 13, a motor frame outer body 14 provided on the outer periphery of the stator 13, and motor frame side plates 15 and 16 which are fixed to both open ends of the motor frame outer body 14 by welding. And a can 17 fitted to the inner peripheral portion of the stator 13 and welded to the motor frame side plates 15 and 16. Further, the rotor 18 accommodated in the stator 13 so as to be rotatable is fixed to the main shaft 7 by shrink fitting. An annular space (flow path) 40 is formed between the motor frame outer body 14 and the outer cylinder 2. An inverter (frequency converter) F is fixed to the outer surface of the outer cylinder (barrel) 2 containing the handling liquid around the motor. The inverter F is accommodated in the case 20, and the case 20 also includes a flow rate indicator and a flow rate setting knob.
[0021]
The motor frame side plate 15 of the canned motor 6 holds a guide member 11 that guides the fluid from radially outward to inward. An inner casing 12 that houses the impeller 8 is fixed to the guide member 11. A seal member 13 is interposed on the outer periphery of the guide member 11.
[0022]
A liner ring 51 is provided at the inner end of the guide member 11, and the liner ring 51 slides on the front portion (on the suction mouse side) of the impeller 8. The inner casing 12 has a substantially dome shape and covers the shaft end of the main shaft 7 of the canned motor pump 6. The inner casing 12 has a guide device 12a composed of a guide vane or a volute that guides the fluid discharged from the impeller 8. Further, the inner casing 12 has an air vent hole 12b at the tip.
[0023]
The bearing is a sliding bearing made of silicon carbide, and all the bearings are accommodated in a space between the motor rotor 18 and the impeller 8. The bearing is lubricated with its own liquid.
The bearing bracket 21 is made of a cast stainless steel, and fixed-side radial bearings 22 and 23 are fixed by shrinkage fitting on both sides in the axial direction. Further, the bearing bracket 21 is stopped by injecting resin from the outer periphery. The axial end portions of the fixed-side radial bearings 22 and 23 are configured to slide with the rotation-side thrust bearings 24 and 25. The rotation-side thrust bearings 24 and 25 and the rotation-side radial bearings 26 and 27 are fixed to the main shaft 7 with a spring stopper nut 29 through an impeller 8 and a distance piece 28 as appropriate.
[0024]
The operation of the all-around flow type canned motor pump shown in FIG. 3 will be briefly described. The fluid sucked from the suction casing 3 is an annular shape formed between the outer cylinder 2 and the motor frame outer cylinder 14 of the canned motor 6. It flows into the flow path 40 and is guided to the guide member 11 through the flow path 40 and guided into the impeller 8. The fluid discharged from the impeller 8 is discharged from the discharge casing 4 through the guide device 12a.
[0025]
Next, an embodiment of the frequency converter in the present invention will be described with reference to FIG. In FIG. 4, a fluid machine such as a pump is indicated by M, and a frequency converter is indicated by F. When three-phase alternating current is used as an input, the frequency converter F includes a converter portion including a rectifier circuit 41 that converts alternating current into direct current, a smoothing capacitor 42 that smoothes the rectified voltage, and an inverter portion 43 that converts direct current into alternating current. It consists of. An auxiliary power supply unit 44 and a voltage detection unit 45 that detects a DC voltage of the converter unit are connected to the converter that is a DC unit. The frequency converter F further includes a control unit 46 that stores in advance the relationship between the generated frequency and the current value, outputs a PWM signal from the control unit 46, and drives the inverter unit 43.
[0026]
A current detection sensor 48 is provided at the output section of the three-phase inverter 43, and the detected current is converted into a signal by the detection section 47 and input to the control section 46. The motor 6 is connected to the output side of the three-phase inverter 43. Reference numeral 49 denotes a temperature sensor.
[0027]
The control unit 46 compares the ROM that previously stores the function for specifying the generated frequency and current value, the signal from the current detection unit 47 and the setting contents of the ROM, performs arithmetic processing, and outputs a predetermined PWM signal. CPU and control IC are provided.
[0028]
The frequency converter F has the control part 46 as mentioned above, and can memorize | store the time which self output. Moreover, if the operation by the above-described constant flow rate control is performed, the frequency converter F can detect the flow rate every moment that the pump is carrying. Further, the frequency converter F has a calculation function. Therefore, the frequency converter F can display the integrated flow rate in addition to the momentary flow rate. That is, the pump device itself can be used as a flow meter.
[0029]
Further, by utilizing the memory function of the frequency converter F, a predetermined amount (for example, 1 m ³ ) of water is transported every predetermined time (for example, 24 hours) for a predetermined number of days (for example, 5 days). For example, it is possible to perform an automatic operation that pauses for two days and performs work continuously for a predetermined number of days (for example, five days). This method is suitable for water saving by limiting the daily water supply amount, and is characterized in that automatic water supply can be performed without providing any special incidental facilities.
[0030]
【The invention's effect】
As described above, according to the present invention, a special auxiliary facility is not required, and a fluid machine such as a vortex pump that constantly supplies a stable flow rate can be obtained regardless of changes in pipe resistance.
Further, according to the present invention, it is possible to realize a fluid machine such as an axial flow pump having a constant generated head even if the flow rate changes.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a basic concept of a fluid machine according to the present invention.
FIG. 2 is an explanatory diagram illustrating a basic concept of a fluid machine according to the present invention.
FIG. 3 is a cross-sectional view showing a pump device suitable for carrying out the present invention.
FIG. 4 is a circuit diagram of a frequency converter in the present invention.
[Explanation of symbols]
1 Pump casing 2 Outer cylinder (barrel)
3 Suction casing 4 Discharge casing 6 Canned motor 7 Main shaft 8 Impeller 11 Guide member 12 Inner casing 13 Stator 18 Rotor 21 Bearing brackets 22 and 23 Fixed radial bearings 24 and 25 Rotary thrust bearings 26 and 27 Rotary radial bearings 41 Rectifier circuit 42 Smoothing capacitor 43 Three-phase inverter 44 Auxiliary power supply unit 45 Voltage detection unit 46 Control unit 47 Current detection unit F Frequency converter M Fluid machinery

Claims (3)

In a fluid machine driven by a motor and rotating an impeller to generate pressure, a frequency converter that supplies power to the motor, a detection means that detects a current value of the current supplied to the motor, and a frequency ( Hz ) And the current value (A) A = K Hz ⁿ (where K and n are positive constants), and a controller provided in the frequency converter that stores in advance,
The control unit compares the frequency and current value in actual operation with A = K Hz ⁿ which is the relationship between the frequency ( Hz ) and the current value (A), and the current of the current supplied to the motor value to so that by changing the occurrence frequency of the frequency converter to match the a = K Hz ^n,
A fluid machine characterized in that the frequency converter is provided with means for switching the values of K and n .   2. The fluid machine according to claim 1, wherein a fluid machine is used in which shaft power increases as the flow rate increases under the same rotational speed, so that the flow rate becomes substantially constant even if the generated pressure changes. Fluid machinery.   2. A fluid machine in which shaft power decreases as the flow rate increases under the same rotational speed, so that the generated pressure becomes substantially constant even when the flow rate changes. Fluid machinery.

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